D-Link DES-3326S Ospf Authentication, Simple Password Authentication, Backbone and Area, 135

DES-3326S Layer 3 Fast Ethernet Switch User’s Guide

OSPF Authentication

OSPF packets can be authenticated as coming from trusted routers by the use of predefined passwords. The default for routers is to use not authentication.

There are two other authentication methods − simple password authentication (key) and Message Digest authentication (MD-5).

Simple Password Authentication

A password (or key) can be configured on a per-area basis. Routers in the same area that participate in the routing domain must be configured with the same key. This method is possibly vulnerable to passive attacks where a link analyzer is used to obtain the password.

Message Digest Authentication (MD-5)

MD-5 authentication is a cryptographic method. A key and a key-ID are configured on each router. The router then uses an algorithm to generate a mathematical “message digest” that is derived from the OSPF packet, the key and the key-ID. This message digest (a number) is then appended to the packet. The key is not exchanged over the wire and a non-decreasing sequence number is included to prevent replay attacks.

The Backbone and Area 0

OSPF limits the number of link-state updates required between routers by defining areas within which a given router operates. When more than one area is configured, one area is designated as area 0 − also called the backbone.

The backbone is at the center of all other areas − all areas of the network have a physical (or virtual) connection to the

Switch Management and Operating Concepts 135